DESCRIPTION: (provided by the applicant): The worldwide resurgence of virulent and resistant forms of mosquito-borne diseases has increased the urgency for novel mosquito control strategies. The long-term goal of the proposed research is to elucidate the molecular mechanisms underlying female-specific gene activity in the immature mosquito in order to develop novel mosquito control strategies by transgenic manipulation. Most studies of sex-specific gene activity have focused on expression in adult insects. In the fruit fly, Drosophila melanogaster, the molecular basis for gene activation in adult females and repression in males is well understood for the transcriptional regulator, Doublesex (DSX). Our studies of hexamerin genes have allowed us to develop a model system to study sex-specific gene activity in the larval mosquito. In holometabolous insects, hexamerins (hexameric storage proteins) are abundantly synthesized by the fat body of late-stage larvae. Recently we showed that one of the hexamerins, AatHex-1 .2, produced by fourth-instar larvae of the mosquito, Aedes atropalpus, is truly female-specific. In the 5'-flanking region of the AatHex-1.2 gene, we identified putative regulatory elements (including DSX binding sites), which we believe govern its tissue-, stage- and sex-specific activity. 700 bp of this region are sufficient to direct 10-fold higher reporter gene activity uniquely in the fat body of female larvae of the heterologous dipteran, D. melanogaster. To elucidate the molecular basis for sexually dimorphic AatHex-1.2 activity, we propose to identify the requisite regulatory DNA sequences and transcription factor binding sites. Regulatory sequences will be mapped by gene transfer in the mosquitoes, Aedes aegypti and Ae. atropalpus, and in Drosophila. Transcription factors will be characterized using electrophoretic mobility shift assays and DNase foot printing. Accomplishment of these aims will not only provide a better understanding of the molecular basis for sex- and fat body-specific gene activity in an insect larva but will also define a minimal promoter to improve the sterile insect technique (SIT) for insect control and to develop novel means for driving transgenes into natural populations.